The invention relates to a process for producing a steel component which is provided with a metallic, corrosion protection coating and has very good mechanical properties, and also a steel component of this type.
A method of protecting steel substrates against corrosion which has been known and proven for many years is melt dip coating of fine metal sheet, in particular fine steel sheet in strip form, in a melt bath containing zinc or a zinc alloy. The layer thickness of the zinc coating is usually set by means of stripping nozzles which are arranged above the melt bath and are directed at the part of the steel strip which runs essentially vertically up from the melt bath. This coating process is also referred to as hot galvanizing.
A variant of hot-galvanized fine metal sheet which has likewise been known for many years is “galvannealed”. This variant is obtained when the steel strip is heat-treated in a furnace after the stripping nozzles, with iron diffusing from the base material into the zinc layer and converting the latter into a zinc-iron alloy layer.
EP 1 143 029 B1 describes a process for obtaining a workpiece having very good mechanical properties, in which the workpiece is formed by hot deep drawing of a metal sheet which has been cut to size. The metal sheet which has been cut to size is cut from a steel strip of the “galvannealed” type. Before the hot deep drawing of the metal sheet which has been cut to size, an intermetallic alloy compound which is intended to ensure protection against corrosion and against decarburization of the steel is produced on the surface of the sheet. For this purpose, the steel strip which has been coated with zinc or an alloy based on zinc is subjected to a heat treatment in which the coated steel strip is exposed to a temperature to above 700° C.
However, visible cracks and pores in the metallic corrosion protection coating are in practice frequently found on fine steel sheet of the “galvannealed” type; these are visible even after surface coating of the fine metal sheet and thus do not satisfy, inter alia, demanding requirements which the surface coating surface has to meet.